SIMULTANEOUS PROCESSING OF SHORT DELAYS AND HIGHER-ORDER TEMPORAL INTERVALS WITHIN A SESSION BY PIGEONS

This study tests the ability of pigeons to process simultaneously two kinds of temporal intervals of the sort relevant in foraging problems: delays within trials on the order of seconds as well as 'higher order ' intervals, on the order of minutes, within the session. Pigeons were given 20 min sessions of a chained VI 5 s-FI 10 s schedule reinforcem ent. A particularly large reinforcer was delivered either after 16 min or after 6 min, in a blocked design. In probe sessions no large reinf orcer was given. The rate of responding in probe sessions following tr aining with the early reinforcer showed a peak in rate of responding a t about 6 min. In probe sessions following training with the late rein forcer, the rate of responding showed only a linear increase. In addit ion, empty trials using the peak procedure showed that the pigeons tim ed the FI 10 s within trials, as predicted by models of timing with tw o accumulators. Baseline sessions with no large reinforcer at the begi nning of the experiment showed a bitonic function with slight changes in rates of responding.